New U-shaped liquid crystals azobenzene derived from catechol for photoswitching properties

Rahman, Md. Lutfor; Biswas, Tanmay; Sarkar, Shaheen M.; Yusoff, Mashitah M.; Malek, Muhammad Nor Fazli Abdul; Tschierske, Carsten

doi:10.1016/j.molliq.2014.12.022

Cited by 27 publications

(4 citation statements)

References 32 publications

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“…In general, the ability of a molecule to form mesophases depends on the combination of a variety of parameters such as dipole moments (induced or permanent), polarizability, structural anisotropy, and the ability to segregate, which makes the prediction of liquid crystalline behavior challenging. ,− However, in a simplified consideration the following discussion will focus on the supramolecular architecture and the permanent overall dipole moment of the investigated HBAs, being aware of the mutual influence of the parameters mentioned above. Structural anisotropy results from the overall shape of the assemblies and the combination of polar/rigid (aromatic) and less-polar/flexible segments (alkyl chains) .…”

Section: Resultsmentioning

confidence: 99%

“…Although a number of hydrogen-bonded systems with liquid crystalline behavior are reported, − the impact of the complex interplay of the noncovalent interactions on the mesomorphic behavior still remains obscure. To shed light into these structure–property relationships, we recently reported a modular approach for a comprehensive study.…”

Section: Introductionmentioning

confidence: 99%

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Structure–Property Relationships in Hydrogen-Bonded Liquid Crystals

et al. 2017

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The structural impact of hydrogen-donating moieties on the liquid crystalline behavior of hydrogen-bonded assemblies (HBAs) is comprehensively investigated. Therefore, a series of phenol derivatives such as phenol, catechol (CA), resorcinol (RE), hydroquinone (HQ), pyrogallol, hydroxyhydroquinone, and phloroglucinol (PHG) were combined with alkoxyazopyridines (Ap-N) yielding 49 new HBAs, which were studied with respect to their mesomorphic properties. The present study revealed significant differences in the liquid crystalline behavior of the structurally diverse assemblies, ranging from the absence of a mesophase to smectic or nematic phases. In contrast to previous studies a comprehensive crystallographic analysis provides insight into the structure–property relationships of the assemblies and proves a correlation between the supramolecular architecture and the macroscopic properties (=liquid crystallinity). More specifically, comparison of the single crystal data with the 2D X-ray diffraction patterns indicates that linear assemblies tend to form crystalline or smectic phases (for the HQ and RE, respectively), while a bent-shaped assembly yields nematic phases (for CA and PHG). Furthermore, our results suggest that segregation of aliphatic and aromatic segments, as observed in the solid state structures, supports the formation of stable mesophases.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structure–Property Relationships in Hydrogen-Bonded Liquid Crystals

et al. 2017

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“…In this case, one mesogenic core is folded back nearly antiparallel to the other mesogenic one (see Figure b). It is called U-shaped conformer and has never been assumed by main-chain polymers and the twin dimer with a pentamethylene spacer, although it sometimes appears when 3-methyl pentamethylene is used as a spacer. , U-shaped conformations were also reported for bent-shaped molecules with an o -phenylene unit within the aliphatic spacer …”

Section: Discussionmentioning

confidence: 99%

“…62,63 U-shaped conformations were also reported for bent-shaped molecules with an ophenylene unit within the aliphatic spacer. 64 Keeping this conformational constraint in mind, let's speculate how the twin molecules with n = 5 can form the N F phase with the polarization along the n-director. At first, one envisages that twin molecules taking a bent conformation form the nematic LC.…”

Section: Discussionmentioning

confidence: 99%

Three Distinct Polar Phases, Isotropic, Nematic, and Smectic-A Phases, Formed from a Fluoro-Substituted Dimeric Molecule with Large Dipole Moment

et al. 2023

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A dimeric molecule, di-5(3FM-C4T), with fluorosubstituted mesogenic cores composed of three-aromatic rings and linked by a pentamethylene spacer is prepared. Di-5(3FM-C4T) forms the ferroelectric nematic (N F ), ferroelectric smectic-A (SmAP F ), and polar isotropic (Iso P ) phases. The N F phase is composed of molecules in U-shaped conformation that behave like polar rod-like molecules. The reversal spontaneous polarization (P s ) is approximately 8 μC cm −2 , which is extremely large and reflects the huge dipole moment (11.2 D) of the one-side mesogenic core. On the other hand, the SmAP F phase is formed by bent-shaped molecules. The N F −SmAP F phase transition thus follows the conformational change of molecules. The reversal P s of the SmAP F phase is around 4 μC cm −2 , which is half of that in the N F phase, and this is an expected value from the bent shape of the molecules. It is interesting that the highest temperature Iso P phase still exhibits the polar structure and possibly retains some polar aggregation of molecules in small domains. The three polar phases exhibit the dielectric mode due to the collective polarization fluctuation at around 100 Hz, giving the high dielectric constant over 8000.

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Alkyl‐Alkyl Interactions in the Periphery of Supramolecular Entities: From the Evaluation of Weak Forces to Applications

Giese

Albrecht

2020

ChemPlusChem

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Supramolecular chemistry is based on weak intermolecular forces which nevertheless are of importance for chemical processes. In this report the relevance of alkyl-alkyl interactions in supramolecular assemblies is discussed. We show how hierarchically formed helicates can be used to evaluate weak interactions of alkyl groups based on solvent-supported London dispersion. In addition, the role of nano-segregation of alkyl groups in the periphery of supramolecular assemblies is described, as well as how this can be used to improve the properties of liquid-crystalline materials by controlling the alkylchain-mediated aggregation process.[a] Prof. Figure 1. Two states of the Wilcox-type molecular torsion balance to estimate the strength of weak interactions between substituents R and R'.ChemPlusChem Minireviews

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New U-shaped liquid crystals azobenzene derived from catechol for photoswitching properties

Cited by 27 publications

References 32 publications

Structure–Property Relationships in Hydrogen-Bonded Liquid Crystals

Structure–Property Relationships in Hydrogen-Bonded Liquid Crystals

Three Distinct Polar Phases, Isotropic, Nematic, and Smectic-A Phases, Formed from a Fluoro-Substituted Dimeric Molecule with Large Dipole Moment

Alkyl‐Alkyl Interactions in the Periphery of Supramolecular Entities: From the Evaluation of Weak Forces to Applications

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